The car bombing was the latest attack to hit Kabul, coming just over a week after a team of Taliban gunmen and suicide bombers staged an assault that paralyzed the city and left 12 people dead. The violence has underscored fears that militants would try to stage attacks ahead of a key international conference on Afghanistan to be held Thursday in London.

The bomber detonated a minivan packed with explosives near Camp Phoenix, an American base inside Kabul, wounding at least six Afghan civilians, said Jamil Jumbish, the head of Afghanistan's criminal investigation unit.

The Taliban claimed responsibility for the attack and said it was targeting an international military convoy, according to a text message to The Associated Press from a phone number commonly used by the militant group.

NATO forces confirmed a car bomb struck outside the main gate of Camp Phoenix, saying it was aimed at a civilian convoy that was entering the controlled checkpoint.

Eight Americans suffered minor injuries, according to a NATO official, who released the information ahead of a formal announcement on condition of anonymity. He did not say if they were troops or civilians.

Four Afghan policemen were killed overnight at a checkpoint near the Information and Cultural Affairs Ministry's directorate in Lashkar Gah, the capital of Helmand province. The southern area is expected to be a major focus of fighting with the influx of 37,000 additional U.S. and NATO forces.

Taliban militants frequently target Afghan security forces and officials to undermine the U.S.-backed government, but authorities said it was not yet clear who killed the policemen.

Daoud Ahmadi, a spokesman for the provincial governor, said said the officers apparently had visitors and an investigation was under way into whether the attack was political or personal.

In eastern Kunar province, a NATO airstrike killed several suspected insurgents who were maneuvering into fighting position in an area previously used to stage attacks on international forces, the coalition said in a statement.

Spokeswoman Maj. Virginia McCabe said between five and 10 militants were killed.

President Hamid Karzai said Tuesday that the London conference offers a major opportunity for his government to present its plans for reconciliation in an effort to drain the insurgency of support.

Musadeq Sadeq
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AP

An Afghan man injured in Tuesday's suicide attack.

Karzai spoke Tuesday in Turkey after a meeting of nations that seek to help Afghanistan emerge from instability with aid, trade, training and political support. Delegates included British Foreign Secretary David Miliband, Chinese Foreign Minister Yang Jiechi and Pakistani President Asif Ali Zardari.

German Chancellor Angela Merkel said Tuesday that her country plans to increase its troop contingent in Afghanistan by up to 850 and focus more strongly on training local security forces.

Germany currently has nearly 4,300 soldiers in northern Afghanistan. They serve under a parliamentary mandate that sets the maximum number at 4,500; Merkel did not specify what the new upper limit might be.

In Kabul, meanwhile, security officials gave the first detailed account of how a small group of militants infiltrated the capital in the Jan. 18 attack on government buildings and a major shopping center, which left five civilians and Afghan security forces dead, along with the seven assailants.

Intelligence officials played a videotape for reporters from a man who allegedly sheltered the seven attackers — all of whom died in the attack. The alleged ringleader — who was arrested a day after the attack — said operatives from the al-Qaida-linked Haqqani militant network ordered him to the capital from his home in eastern Nangarhar province.

"I received a phone call telling me to come to Kabul," said Kamaluddin, who like many Afghans goes by one name. "The plan was organized by a commander for Jalaluddin Haqqani."

He said a man named Bashir explained that he would bring seven suicide bombers and Kamaluddin was to keep them in a house he rented in the city and help organize the attack — including painting a vehicle loaded with explosives to look like an ambulance.

Kamaluddin supplied the bombers with suicide vests and ammunition, said Sayed Ansari, a spokesman for the Afghan intelligence service. He said they were still trying to identify the lead bombers in the attack.